Methane production and colon cancer.

The cause of the high incidence of methane producers in patients with colorectal cancer is not clear. A total of 270 individuals were studied for methane production, using an end-expiratory breath sampling technique. They were divided into eight groups: 156 healthy controls (group 1); 47 patients with colorectal cancer (group 2); 36 patients (34 of them included in the previous group) after resection of the tumor (group 3); 7 (also included in group 2) with nonresectable tumor (group 4); 29 with nonmalignant diseases of the colon (group 5); 12 with extensive ulcerative colitis (group 6); 12 with ulcerative proctosigmoiditis (group 7); and 12 with colonic polyposis (group 8). Significantly more patients (91.4%) with colorectal cancer in group 2 produced methane than either healthy controls (42.9%) (p less than 0.001) or patients with benign diseases of the colon (41.3%) (p less than 0.001). In 36 patients (group 3) in whom the cancer was resected, the incidence of methane producers fell to 47.2%, similar to the control group, but significantly different from group 2 (p less than 0.001). The percentage of methane producers in patients operated on, but with unresectable cancer, remained very high (87.7%). A significantly higher proportion of patients with extensive ulcerative colitis (group 6) and colonic polyposis (group 7) produced methane than patients with ulcerative proctosigmoiditis (group 7), benign diseases of the colon (group 5), and healthy controls (p less than 0.05). The results suggest that the presence of cancer in the large bowel directly influences methane production. In addition, in the group of diseases with a high risk of malignancy, the prevalence of methane-producing individuals was significantly higher than in the healthy population and in patients with benign diseases of the colon.